It is well known in carton packaging machines to utilize segment wheel assemblies to pick single carton blanks from a magazine of back-to-back blanks and position the blanks on a conveyor. The conveyor generally then transports the carton blanks to in a single file end-to-end relationship to an area of the packaging machine where they are folded around or packed with articles such as, for example, beverage cans. U.S. Pat. No. 6,497,084 of Janen, which is owned by the assignee of the present invention, discloses a carton blank transport apparatus that includes a traditional segment wheel assembly and conveyor for the aforementioned use, and this patent is hereby incorporated fully by reference.
FIGS. 1 and 2 below illustrate in somewhat simplified form a traditional and well known prior art segment wheel assembly found in carton packaging machines. The prior art assembly 11 comprises a first segment wheel 12, generally in the shape of a disc, and a similar second segment wheel 13, that are mounted in spaced relationship on a rotatable segment wheel shaft 14. The segment wheel shaft 14 is continuous and extends between the segment wheels 12 and 13. The segment wheels 12 and 13 ride on respective nip rollers 22 and 23, which also are rotatable. As shown in FIG. 2, each segment wheel is formed with a somewhat crescent-shaped cut-out 26 for purposes detailed below.
A pair of pick arms 16 and 17 are mounted on a pick arm shaft 18 disposed above the segment wheels. The pick arms extend downwardly between the segment wheels and are provided at their lower ends with suction cups 19 and 21. Of course, associated suction lines, side plates, bearings, sprockets, and gears are associated with the segment wheel assembly 11 to operate the assembly as described below. Such associated machinery is well known in the art and thus need not be described in detail here.
FIG. 2 illustrates typical operation of the prior art segment wheel assembly an is a view taken along line A-A of FIG. 1 so that only segment wheel 13 and pick arm 17 are shown. It will be understood that the other segment wheel and pick arm operate identically. In operation, a horizontal back-to-back stack of carton blanks 32 is located in a magazine adjacent the downstream end of the segment wheel assembly. The segment wheel 13 is rotated in a counterclockwise direction at a predetermined speed, as indicated by arrow 28, while the nip roller 23 is rotated in a clockwise direction as indicated by arrow 29. As the segment wheel and nip roller are rotated, the pick arm 17 is articulated back and forth by the articulating pick arm shaft 18, as indicated by arrows 31. The range of articulation is predetermined so that the suction cup 21 swings toward and contacts a carton blank on the end of the stack 32.
The suction cup grabs the end blank of the stack and, as the pick arm begins to articulate back, pulls the blank to the right in FIG. 2 against the rotating segment wheel 13. The timing of this motion is such that the cutout 26 of the rotating segment wheel 13 passes the top of the carton blank, which drops into the cutout. The pick arm then releases the blank and articulates on up to the right and out of the way. As the segment wheel continues to rotate, the lip 27 of its cutout 26 pulls or urges the top of the carton blank down against the rotating nip roller 23. The blank then becomes captured between the nip roller and the segment wheel and is thereby drawn to the right and delivered to a conveyor (not shown), which conveys the blank to the right as indicated by arrow 33 to be delivered to a packaging area of the packaging machine. The just described motion of the segment wheel assembly repeats over and over. In this way, carton blanks are drawn one at a time from the stack 32 and delivered in single file edge-to-edge relationship to the conveyor.
While prior art segment wheel assemblies have proven reasonably successful, they nevertheless have been plagued with various problems and shortcomings inherent in their designs. The most serious of these, perhaps, is the fact the pick arm must be highly curved and convoluted as shown in FIG. 2 in order to avoid hitting the segment wheel shaft 14 as the pick arm articulates. A closely related problem is that the lower end of the pick arm and thus the suction cup 21 also must be located relatively low so that it does not hit the segment arm shaft during operation. This means that the suction cup necessarily engages and grabs the carton blanks of the stack at a location substantially below the top edges of the blanks. This, in turn, causes a number of problems. For instance, since the blanks are being pulled against the segment wheels from a low position, substantial bowing of the blanks as they engage the segment wheels can occur. This bowing can cause flaps in the blank to pop open, misalignment of the blanks as they are delivered to the conveyor, and even machine jams on occasion. It would be much more desirable to grab the carton blanks nearer their top edges where end flaps typically are located. However, this has not been possible in the past because of the requirement that the suction cups clear the segment wheel shaft 14 as they move back and forth.
Accordingly, a need exist for an improved segment wheel assembly in which carton blanks are picked from a stack at or near their top edges rather than nearer their middle portions. More generally, a need exists for a segment wheel assembly wherein suction cups of the pick arm assembly can be positioned to engage blanks at any desired location. A further need exists for a segment wheel assembly with a simpler, more space efficient, and less convoluted pick arm configuration. It is to the provision of a segment wheel assembly that addresses these and other needs that the present invention is primarily directed.